Oleum Foeniculi. Oil of Fennel.

Related entries: Fennel

Oil of fennel is obtained by distillation from the dried ripe fruit of Foeniculum vulgare, Mill, also known as F. capillaceum, Gilib. (N.O. Umbelliferae), a plant cultivated in Germany, Russia, Japan, etc. It is official in the U.S.P. It occurs as a colourless or slightly yellow liquid, having the characteristic aromatic odour of fennel, and a taste at first bitter and camphoraceous but afterwards sweetish. The alcoholic solution is neutral to litmus, and is not coloured by the addition of ferric chloride solution (absence of oils containing phenols). Specific gravity, 0.960 to 0.990 (0.953 to 0.985 at 25°); optical rotation, +6° to +20°; melting-point, usually between 5° and 10°, but should not fall below 4°. The characteristic fennel odour is due to the anethol and fenchone it contains. Oils deprived of some of their anethol by freezing or fractionation have their congealing point lowered, while the addition of alcohol or turpentine may be suspected from the lowering of the specific gravity.

Soluble in an equal volume of alcohol; in 80 per cent. alcohol (1 in 5 to 8).

Constituents.—The chief and most valuable constituent of the oil is anethol (50 to 60 per cent.), which crystallises out in the cold. It also contains 18 to 20 per cent. of fenchone (C₁₀H₁₆O), a ketone isomeric with camphor, strongly dextrogyrate, and convertible into fenchyl alcohol by sodium. Anethol is usually in greatest proportion in those oils containing the least fenchone. The following bodies may also be present in the oil:—Fenchol, d-pinene, dipentene, phellandrene, and limonene.

Action and Uses.—Oil of fennel is an aromatic carminative to the gastro-intestinal tract, and is employed with purgative medicines to prevent griping, and also in the intestinal colic of children as Aqua Foeniculi.

Dose.—¼ to 2 decimils (0.025 to 0.2 milliliters) (½ to 3 minims).

PREPARATIONS.

Aqua Foeniculi, U.S.P.—FENNEL WATER, U.S.P.

Oil of fennel, 0.2; purified talc, 1.5; distilled water, to 100. Average dose.—16 mils (4 fluid drachms).

Aqua Foeniculi Concentrata, B.P.C.—CONCENTRATED FENNEL WATER.

One part of this solution corresponds to 40 parts of fennel water.

The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.